1. Field of the Invention
The invention relates to a printed circuit board (PCB) for a light emitting diode (LED) and a method for producing the same, more particularly to a concave cup PCB for the LED and a method for producing the same.
2. Description of the Related Art
Referring to FIG. 1, a conventional round concave cup PCB for the LED primarily includes a substrate 11, a plurality of round concave cups 12 formed in the substrate 11, and a plurality of conductive foils 13 mounted on the substrate 11. The method for producing the conventional round concave cup PCB includes the steps of forming a plurality of round concave cups 12 on a surface of the substrate 11, and mounting the conductive foils 13 on the surface of the substrate 11 so as to produce the round concave cup PCB.
The round concave cup PCB can be further processed to produce the LED. Referring to FIG. 2, a diode die 14 is fixed on a flat bottom of each of the round concave cups 12 by adhesive dispensing, and the dies 14 and the conductive foils 13 are electrically connected through conductive wires 15 by wire bonding. Finally, a packing layer 16 of an epoxy resin is formed on the substrate 11 so as to conceal the dies 14, conductive foils 13 and conductive wires 15 therebeneath and to produce the LED product.
It is known that the aforesaid LED product has a better heat dissipation because the dies 14 are directly buried into the round concave cup PCB that has the advantage of good heat dissipation. In addition, the LED product also has better control in light amplifying ratio and better effect in light mixing because the dies 14 of different colors can be implanted into the round concave cup PCB.
However, one of the main disadvantages of the prior art resides in that it involves a lengthy and complex manufacturing process. Furthermore, due to the involvement of too many processing steps, the possibility of processing error, which leads to yield loss of the end product, is higher.
In the prior art, the substrate 11 for the round concave cup PCB has to be drilled by computer numerical control (CNC), and then by a special miller cutter having a tip of a concave cup configuration to mill the round concave cups 12. After the completion of drilling and milling, the substrate 11 has to be polished, and numerous plating processes (such as copper plating and nickel plating) are then conducted in order to create the reflective concave cup wall and the necessary electrical traces and contacts. In summary, more than twenty steps are involved in the manufacturing process of the prior art. The drilling and milling steps are very tedious and expensive, and any error caused by the drilling step will affect the overall performance of the round concave cup PCB. Moreover, the miller cutter is easily worn off, and has to be replaced periodically because a worn cutter will not produce a smooth cup wall. The uniformity of light reflection can be negatively affected if the round concave cup PCB without a smooth cup wall is subsequently plated with metal coatings. Furthermore, the cost of the cutter and the down time of the machine will incur extra costs in the manufacturing process of the prior art.